1. Field of the Invention
This invention relates to a unique foliar fertilizer formulation and method of applying same to legumes such as soybeans, cereal grain crops, such as corn (maize), and other crop plants such as cotton, potato, tomato and the like. More particularly, this invention relates to foliar fertilizer formulations and methods which provide outstanding increases in yield of field crops by delaying the onset of senescence.
2. Prior Art
Senescence or aging is the metabolic degradation of the biochemical machinery in the vegetative tissues of plants. It is disclosed in L. D. Nooden and S. J. Lindoo's What's New in Plant Physiol, 9(7), 25 (1978), that senescence in plants is probably initiated by a hormone-like substance which travels from the fruits to the leaves and other vegetative tissue. With the onset of senescence, the ability of vegetative tissues to assimilate nutrients from foliarly-applied fertilizers and to translocate other nutrients which may be present in the vegetative tissues to the reproductive tissues or crop declines. This results in a discontinuation of crop growth and no further increases in yield. Several beneficial effects on crop yield would result if the onset of senescence could be delayed. For example, a delay in senescence would maintain the nutrient assimilative capacity of the vegetative tissue of the plant, and allow such tissue to translocate such nutrients and any other nutrients which may be within the vegetative tissue to the reproductive tissue. The net result is an increase in the total assimilation and a transfer of more nutrients from the vegetative tissue to the reproductive tissue or fruit, all of which provides for increased fruit size and/or number and yields.
Several plant growth regulators have been used to delay senescence. For example, in D. J. Osborne, Symp. Soc. Exp. Biol., 21, 305(1967), it discloses that cytokinins are the most generally effective class of senescence-retarding plant growth regulators. Similarly, L. D. Nooden, G. M. Kahanak and Y. Okatan, Science, 206, 841 (1979) disclose the use of a mixture of naphthalene-acetic acid and benzyladenine for delaying senescence in soybeans. (Also see Nooden, L. D. and A. C. Leopold, pp. 329-368 in Phytohormones and Related Compounds, Vol. II, D. S. Letham, et al, eds. (1978)).
In foliar feeding of plants, the nutrients are dissolved in water and the aqueous solution of nutrients is sprayed on the leaves of the plants. U.S. Pat. No. 3,087,806 describes a method for improving the yield of soybeans by spraying the plants periodically throughout their growth with an aqueous solution of urea phosphate. The patent recommends twice weekly applications; and in an example such twice weekly sprayings were carried out for a period of 18 weeks.
U.S. Pat. No. 3,558,300 describes a method for foliar feeding of field crops, including soybeans and cereal grains, with an aqueous solution of an ammonium polyphosphate. Adequate soil fertilizer is employed in conjunction with the foliar feeding. It is claimed that the method improves the stress resistance of the plants. The ammonium polyphosphate solution is described as being applied during the crop growth period up to the flowering period.
U.S. Pat. No. 4,038,064 describes a foliar fertilizer composition containing urea, water, potassium, phosphorus in the form of linear polyphosphates, and micronutrients such as sulfur, boron, zinc, iron, manganese and copper. The patent also describes a process of improving soybean plant yields by applying the composition to the foliage of the soybean plant. The patent states that the composition must be applied during the period from shortly before flowering to shortly after the beginning of seed fill.
U.S. Pat. No. 4,146,383 describes a method for improving the yield of legume field crops and cereal grain crops by applying a foliar fertilizer composition containing sources of nitrogen, phosphorus, potassium and sulfur to the foliage of the crops during the seed-filling period. The patent specifies that prior to the seed-filling period, nutrients are supplied to the growing legume and cereal crops exclusively from the ground.
U.S. Pat. No. 4,033,146 describes a method of fertilizing conifer forests with nitrogen containing compounds by direct aerial application to the conifer foliage of an aqueous solution containing a nitrogen source, such as urea, ammonia, and nitrates of ammonium, calcium, and potassium; ammonium phosphates and sulfates; or any combination. The patent states that other micronutrients including iron, manganese, copper and zinc can be added to the solution.
U.S. Pat. No. 4,033,747 discloses a method of fertilizing conifer forest by direct application to the foliage of the conifers of a solution containing a water-soluble nitrogen source. The patent also states that the solution may include sources of calcium, potassium, phosphorus, sulfur and minor trace metal nutrients such as iron, cobalt, molybdenum, manganese, copper, boron, zinc, magnesium and mixtures thereof.
It has been reported that mixed results have been achieved with foliar fertilization of crops, especially field crops and more particularly soybeans. While some tests suggested that yield improvements could be achieved, others suggested that no improvements at all were realized from foliar application of nitrogen-phosphorus-potassium (N-P-K) solutions. The January, 1969 issue of "World Farming" contains a more complete dissertation of the benefits of N-P-K foliar fertilization and the limits of application level beyond which leaf scorch occurs. Another article reprinted from Ohio Farm and Home Research, Vol. 41, No. 302, September-October, 1956, reports no benefit from foliar application N-P-K solutions.
Unsuccessful attempts to increase crop yield by foliar fertilization have been reported by Mederski and Volk for wheat, corn, soybeans, oats and alfalfa. When the field crops were grown in soils with adequate fertility, they failed to respond positively to foliar sprays containing N, P, and K. (Mederski, H. J. and Volk, G. W. Foliar Fertilization of Field Crops, Ohio Agr. Exp. Sta. Research Cir 35, (August 1956).) It has been generally assumed that legume and cereal grain crops which have adequate soil fertilization will not produce significantly higher yields of the grain by supplemental foliar fertilization, although it has been recognized that the nutrients in the spray are absorbed by the leaves of the plants.
It is disclosed in the prior art that mixtures of foliar fertilizers and cytokinins accelerate senescence. For example, in Neumann, P. M. and Giskin, M., "Late Season Foliar Fertilization of Beans with NPKS: Effects of Cytokinins, Calcium and Spray Frequency", Comm. In Soil Science and Plant Analysis, 10(3), 579-589 (1979),it discloses that sequential application of solutions of NPKS and benzyladenine to the foliage of bean plants during pod fill (Phaseolus vulgaris, var. Bulgarian) accelerated leaf senescence and did not increase yield beyond NPKS treatment.